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Saturday, 14 July 2012

UFOs in the Sunset

From Peter C.: "I have just started using an Olympus E-PL2 with 14–50mm standard lens. This was taken two days ago in the evening.

"I'm pretty disappointed. I assure you, those red dots were not UFOs in the sky. This seems to me to be internal flare off the sensor itself, since the sensor looks red when you have the lens off. Notice the regular pattern to the dots.

"Hasn't this ever happened to anyone else? I've never seen it mentioned.

"The camera is brand new and the lens is brand-new clean, only six days old. I wasn't using any filter.

"This doesn't turn me right off the camera, but clearly I can't use it for sunset shots. I'll have to try my K-5 in the same situation. Probably will do tonight although the sky is clear blue coudless today (heh heh, in mid-winter).

"This new camera probably qualify in Australia as 'unfit for purpose' or 'clearly faulty,' but I'm not going to return it. Just very surprised, that's all."

Mike replies:That's just lens flare, and a nice example of it. The sun is pretty high in the sky there and hence still plenty bright. Most lenses, especially zooms, will flare in that situation in one way or another. In this picture you are able to see it because the flare is against the dark clouds; if those red "dots" had been against red "sunset" sky, you might not have noticed them. The color of the flare might possibly be different with a different sensor or with film, but this isn't primarily a sensor artifact. It's coming from the lens. My guess is that there's nothing wrong with your camera or lens—you just chanced upon a situation where the lens flared and you were able to see it easily.

Funny, but back when I got into photography, it used to be assumed that pictures with the sun in them would show flare; now, coatings are so good that people can have the opposite assumption.

If I were you I would continue to use your new camera and lens and keep watching your results—you will soon learn when and where you're likely to encounter flare. It can be an interesting investigation, and useful to know. It's all part of getting to know your lens.

The next evening Peter photographed a completely different sunset with his Pentax K-5 and got no flare, but I suggested that that was a bad test—the subject might be nominally the same according to our conceptions (category "sunset") but the conditions in each shot are completely different. To know what's going on, I suggested he photograph each evening's sunset at the same time with both cameras and compare the results. An even better idea would be to make three shots, using two different lenses on the Olympus, since that would indicate the contribution made by his main lens more easily.

Today's lenses let you include bright light sources in the frame with impunity. Half a century ago, it would have been one of those things photographers would have learned to avoid. Here of course the sun is behind some cloud, but it was a lot brighter than the rest of the sky. I've owned lenses in the past that would have done nasty things with an off-axis bright spot like this. (Note that there are some JPEG artifacts around the sun in this little screen JPEG. They aren't there in the original).

There are all sorts of little tricks you can employ to keep flare at bay, for instance putting the sun behind a little feathering of cloud to reduce its intensity. (This picture was taken with the OM-D's standard zoom, yet it's one I probably wouldn't have tried with my Zeiss 50mm ƒ/1.4 of 30 years ago.)

You can also play with flare. There have been times I've actually been a little disappointed with the high flare resistance of today's lenses—older lenses sometimes do things that are funky, surprising and nice with flare; they at least entertain you. The super-competent coatings of today put up an impressive fight against flare of all kinds.

Surprisingly, one of the toughest forms of flare for lenses to deal with, and consequently a great torture-test for lenses when you're learning about their flare characteristics, is bright off-axis window light in interiors. The flare will impinge on masking structures, of course (i.e., the window casing and muntin bars in this shot), but the test is to see how much veiling glare carries over to the rest of the picture. Although this is the zoom again (the OM-D's standard M.Zuiko Digital ED 12–50mm ƒ/3.5–6.3) it recovers nicely from the influence of the flare source, showing good contrast in the bench and wall lamp in the hall.

These four shots are from the reject pile from my recent vacation, all taken with the OM-D E-M5. They're all camera JPEGs save the last one.

Mike(Thanks to Peter)

UPDATE: I see various readers have pointed me to various "known issue" forum threads here and there about the so-called "red dot" issue. Okay. I'm certainly not going to insist I'm right about this, for the simple but very good reason that I might not be. For every camera system, real (as opposed to, say, software-generated) artifacts are a system-dependent result; you can only rule out contributors if you remove them and find that the results persist.

However, flare is the proximate cause here, in my opinion, regardless of how the system manifests it.

I'm sure I've seen "red dot type" flare with film cameras. But then I've seen all kinds of flare artifacts over the years. Some are characteristic (enough so that software can now fake generic effects), and some are truly bizarre (one friend's camera created a small reddish "C" shape in exactly the same place in about one out of every dozen frames, for no apparent reason and without apparent pattern. Numerous experiments couldn't reproduce the cause and numerous attempts at camera repair didn't help). But it's all flare, folks—non-image-forming light getting through the lens and rattling around in the lens-camera system somehow, bouncing off things it's not supposed to be bouncing off of and making gremlins.

So it's flare. Who cares how exactly it manifests itself or exactly what it looks like? You can get flare with any camera and lens if you try. No optical system is devoid of it.

I might also gently point out here that forums aren't the right place to "decide" technical issues, because all they do is create group consensus. Short or long disputations end up with people agreeing to agree, or perhaps continuing to disagree with the majority helping to enforce the group's preferred determination or choosing to support the group's leader or leaders, or perhaps deferring to whomever has the best-sounding explanation (and I've seen examples of conclusions that were extraordinarily well-developed at great length and effort that were utterly, completely wrong) or even whoever's been hanging around the forum the longest (because they can say things like "we've discussed this many times before and here's what we decided"). Forums can often engage in long, fanatically detailed, partially researched, closely reasoned epic arguments that culminate in a strange "folk" conclusion that real experts simply roll their eyes at. (I say that not to claim that I'm a real expert, but because I've known those who are.)

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Featured Comment by Jeremy Fagan: "Some people pay a fortune for a red dot on their camera. Count yourself lucky to have so many...."

Featured Comment by Tim Parkin: "I'm pretty sure this is a microlens phenomenon.... Yes it's flare but of a particular type to digital cameras. You can even see the variation in brightness across the bayer array. here's a diagram from this page...and here's some great research on it with examples of different focal lengths."

I think Mike is incorrect on this, not simple lens flare but the "red dot" issue that some have reported with one or more of the Pens. Google Olympus red dot or red spot and you will find a bunch of discussions. I have never seen it myself ( E-PL2, E-M5), but I've never shot directly into the sun.....

An even better idea is to turn the camera around and photograph the light that such beautiful sunsets cast for just a few moments! Flare problems gone!

I agree that it looks like flare to me, too. Lens coatings really have become extremely adept at minimizing flare during the digital age. A couple of weeks ago I was using an old Canon FD lens and was really struck by how flare-prone it was, especially it seemed in LED lighting. I had to be -very- careful not to pick up a ding and also to avoid any glare from my subject. We've come a long way in the lens design and coatings arena!

The other remark I wanted to make was regarding how funky today's lens flares are compared to the old-time lenses. Look at Peter's sample, the rectangular pattern displayed. I was accustomed to the angular repetition of colored cusps that moved from the lens center as the light source/lens relationship changed. But I've noticed odd patterns like this on relatively new camera designs. Perhaps it's the newer lens designs? Perhaps the sensor really is also involved (since, unlike film, it's loaded with little lenses). Whatever the engineering explanation, today's flare is not your grandpa's flare!

Like Mike, I'm also kind of disappointed that modern-day coatings are super competent against flare; back then we had to guard against it even in the studio, using hoods and flags and whatnot. We learnt to use it creatively.

Of course, these days, people use Photoshop to add in "creative flare". Which is nothing like the real thing and overhashed....crap.

I don't think anyone has provided a satisfactory explanation, although I lean toward Mike's lens flare version. Flare can result from reflections from any surface so red reflections from the sensor could be the cause.

Beautiful lens flare. I think this makes the photograph interesting. I would explore it more. The iPhone has some unique flare. I have been exploring it for some time now. I have found that when taking a photograph with the bright sun in it exposing for something else other than the sun you get this beautiful flare.

Noto to editor: I don't know if this is appropriate for this blog, but I'm including a link only to illustrate my point, not for self-promotion.

Those red dots in the first pic definitely do not look like lens flare. More like a reflection off a focus screen or sensor or something. Lens flare would have a single set of reflections on a single axis, generally, not multiple reflections around multiple axes....at least in my experience.

Actually, it isn't flare as such. The E-PL2 is, as is some other cameras, such as the Sigma DP1, known to produce this pattern of red dots when shot against the sun. Apparently the fault lies with some part of the sensor and is not related to the lens, as is ordinary flare.

I'm not convinced that the red dots are due to lens flare. The number of dots, and their regular spacing in rows and columns, hints at some effect from the sensor array. I hope Ctein has a theory on this.

Interesting article, thanks. I have a very nice, very flare-prone Olympus 7-14 zoom (14-28 full-frame equivalent). It flares dramatically anywhere near the sun, and of course anywhere pointed away from the sun you can see your shadow, so that leaves a little sliver of shot possibility with neither. Or cloudy days. But it sure is sharp.

This particular type of flare appears to be more common in digital cameras. I encountered particularly ugly - by that I mean unattractive aesthetically - flare when I had Nikon D100/200/300s and Nikon zooms, esp the 18-200. I remember some discussion starting ~5-6 years ago regarding this and it may be a result of reflections off the sensor or filter back to the rear element of the lens. I searched and found many discussions on this topic.
You may find this 2005 article interesting: http://www.shutterbug.com/content/digitally-optimized-zoom-lenses-do-they-really-make-difference
Remember that film is quite non-reflective and very diffuse, but some of the elements in the sensor can be quite reflective. Fresnel reflection off the boundary of glass and air is ~5%!
I wonder if the D800 and D800E are different? That would tell us a lot.

I'm with you 100% on this one. The technicalities don't matter. (Yes, I am pretty sure I understand what causes this and no I'm not going to discuss it because it DOESN'T matter. It's an irrelevancy.)

This isn't an “issue,” it isn't a “problem,” it isn't a “defect.” It's just something that happens on occasion that falls under the heading of “cameras can't make good photographs of everything you see.” Anyone who thinks a camera should never fail to make a satisfactory photograph under any circumstance, else it be deemed faulty, had better give up photography now. There has never been such a camera and there isn't one yet. Maybe there will be in the future, but in the meantime, take up painting.

Understand I'm using "camera" very loosely here: I really mean cameras, camera bodies, films, digital sensors, and lenses. The whole shebang that goes together to make a photograph. They're not ideal. There will be times when they fail. Those times aren't very often anymore. I probably run into those times more than most, because I'm always trying to figure out what I can get away with. What you do about those times is to learn to avoid them; It's part and parcel of learning what your equipment can and can't do. That's been inherent to the craft since day one; learning what your equipment can and can't do for you.

I am just asking here without commentary: Mike, would that veiled flare in your indoor shot be reduced if you had a polarizer over the lens? So would a polarizer on the first photo remove the red dots from the images?

I am reading the 1938 Kodak book on Polarizers to refresh my approach on some upcoming product photography. Kind of a fun read with it mentioning the recent first practical film polarizer developed by a "Mr. Edwin H. Land". Given his number of patents, how many of his photographic developments, beyond the cheaply manufactured polarizer, are still in use?

I once brought my Nikon D300 and the D3 to a family gathering, one shot with the D300 showed flare in a dark hotel foyer with large windows directly behind the subject. Swapped the D300 for the D3 with the same lens, a 50mm f1.4 afd, and there was no flare, this led me to surmise that there was a difference in the coating on the sensor. Either that or possiblely a different refraction index on the low pass filter.

The little Olympus is an inexpensive camera, so the sensor coatings might be added within specific tolerances in order to keep the price per sensor down. The voigtlander m lenses give off lovely flare, very dreamy...

I took another look at the original photo and have a thought - inspired by optics classes many year ago. The regularity of the ghosts look suspiciously like diffraction. Note how the ghosts are all on a grid? That's indicative of diffraction. Shooting into the sun means you will have minimal exposure with the smallest aperture which is what causes diffraction. The shorter lens focal lengths of some of these digital cameras means that apertures are smaller. Does Peter C. know what the camera settings were?
Want to see what diffraction can look like:http://www.flickr.com/photos/close2far/3276646969/

All the sun / lens flare I'm familiar with takes the form of images of the aperture on a single axis passing through the center of the image circle and the image of the sun, so unless he's using an something like an imagon, I don't think that's lens flare.

I would guess that it is a signal processing artifact. I bet those spots have something to do with a combination of interger overflow in the raw data compression exaggerated by tone mapping in the post processing.

With all due respect for some people, but a reality check is needed here. The lens costs what, $200 extra as part of a kit, it's pointed straight at the sun (in a place where the sun is bright, I might add as a true northerner), a flare phenomenon happens and people are all over it on the net. Seriously, focus on photos themselves or start a long cycle of purchasing lenses that cost four figure sums; no lens and camera system is perfect. I was trying out a $5000 kit yesterday and yes, it had technical faults, but I would still classify it as a superb kit; there are always compromises.

The second thing is that if people start saying that it's not flare then please explain concisely but accurately what you think it is then. I do have a science degree, I'm seeing a purely optical phenomenon and would genuinely like to hear if there is compelling evidence that it is something else.

Well, looking at that again on a monitor larger than my iPhone, it looks a little irregular to be bit wrapping in the signal processing , but unless there is some repeating rectangular grid structure in the lens, it's coming from somewhere else.

I've seen weird non circular lens flare from an old C-mount Angenieux lens with a beamsplitter viewer where the reflections from the focusing aid would show up on film, and some whacky artifacts of the compendium hood on a Hasselblad but without some sort of unusual accessory filter or rectangular lens hood that is generating a refraction pattern, this is coming from behind the lens.

Here is a vivid example of an intense red-dot pattern that showed up on an early-morning shot I took with the Canon s90. That's not all, in addition to the symmetric pattern of red dots you can see veiling flare, ghosting flare, and 6-point diffraction star from the aperture.

My Tamron SP 17-50MM F/2.8 Di II LD Aspherical (IF)has significantly less flare than any of my other 3 lenses, all Minolta from the the early 80's. When shooting under conditions that will cause flaring, I either expect it or take precautions to avoid it, Sometimes it works other times it doesn't.

My field is/was electronics. I don't know enough to be sure or give an explanation, but I still think it's a sensor artifact rather than just lens flare. It's my gut feeling here, and I've got plenty of gut!

The regular pattern to the dots is not like any lens flare I've ever seen. I'm now going to my files to dig out all the examples of flare I can find. I have one absolute beauty in mind right now. It's flare I liked enough to deliberately aim for it. Coming up asap.

Jeremy Fagan, desirable red dots :-) Like it, like it. Trouble is, they need to be visible to everyone else. I know, I may make my own logo out of this pattern.

More on the diffraction pattern theory:
I couldn't stop thinking about this so I did an experiment. I set the aperture of a Oly 14-42 lens to f/22 at the shortest focal length and shot a picture of it. (http://www.jimhayes.com/photo/Oly-Lens.jpg)
The aperture is about 1mm and looks hexagonal. That's very small.
Note in the photo above the sun is right in the middle of the photo and the red dots are surrounding the central image of the sun symmetrically. The red dots also appear to be about the same size as the sun. When the sun is so low on the horizon, the image of the sun is quite red due to the high attenuation of the bluer light in the 6-7 air masses (6-7 times the path length of air one would see looking straight up). Diffraction images are generally bright in the center and get fuzzier to the edges. I'm betting this is a diffraction pattern.
I'll bet you will see this pattern anytime you shoot directly into the sun, but unless the sun is peeking though dark clouds you may not see it.
In normal shooting, the same phenomena occurs but it only causes a slight blurring of the image because it's integrated across the entire image.
Finally, I searched for some references but most require some knowledge of physical optics. However this animation may be interesting http://www.youtube.com/watch?v=Txgo5Nsv4Lg

I've seen this type of flare before (red dots, repeating pattern, when bright sun is in frame.) It occurred from time to time with a friend's cameras, a Canon 550D and later a 50D. They both flare the same way with the sun in the frame.

I haven't played with her cameras often enough to find out whether the flare is due to the lens or the sensor, though.

First a brief note on this statement: "...forums aren't the right place to "decide" technical issues, because all they do is create group consensus."
It's absolutely true, as is the conclusion that sometimes consensus is often erroneously obtained. One example is the conclusion that there is an "equivalente aperture", analogous to what happens with crop factor, so that an f2.8 aperture with translate to f5.6 when the lens would be mounted on a micro 4/3 camera. It's rubbish, of course - but a wide spread one.
More to the point: if my readings are anything to go by, the red dot issue is a kind of flare unrelated to the heavily blown light shown in the last photograph, as they might have different causes. The latter could be a result of digital dynamic range, in that the sensor has a linear response, as opposite to film's smoother and more extended DR curve. Hence the tendency shown by digital cameras to clip highlights easily. (Cf. Michael Freeman, 'Mastering Digital Photography', Ilex, p. 627.) However, this theory must be taken 'cum grano salis': as in all areas of human knowledge, nothing's written in stone.

This is been a 'major' issue with Sigma's compact cameras (DP1, DP2) for a long time. My guess is that it's a combination of internal reflections playing off of the microlenses, and the IR cut filter may be contributing to the coloring. It's interesting in that the Sigma has no OLP filter, and it's IR filter is not bonded to the sensor (but rather sits farther up in the optical path).

Cheers to Ctein. Not only did he write what I was thinking, he did it better as well.

I'm curious as to whether the OP is "pretty disappointed" in Olympus or himself for not choosing equipment better suited to his preferred subject matter. My guess is the former. Since "red dot hysteria" has been forum fodder for months, perhaps it should be the latter? I bet his local camera store would have gladly let him shoot into some strong lights (and what better place to find them!) to simulate this type of backlit shot.

Totally unrelated (but related to the post title, which got me excited). Isn't it interesting that UFO sightings have dramatically decreased now that everybody has a camera with them ALL the time, and that cameras can shoot at incredible ISOs?

I've been using an E-PL2 as my primary camera for about 18 months and I've had the "Red Dots" show up a few times and I've even tried to cause it a few times. My experience breaks down this way:

1. The problem seems to be the worst with small apertures. I never notice it a f4 or larger. I do see some red flare occasionally but no distinct pattern.

2. The problem seems to be worse at longer focal lengths. It is much more likely to appear and be noticeable with a 45mm lens than a 17mm lens.

3. The problem also seems to be worse with a very strong light source with a lot of red in the light surrounded by a darker area. Sun through the clouds, a single bright light in a dark room, the sun between two trees all see to show the pattern more than a low sun on a clear day. It may be there other times but not enough to be noticeable but it does require a strong light source. I have never had the problem with mercury vapor or fluorescent lights.

I had an E-PL1 and I have an E-PM1 and don't get the red dots under the same general conditions. Since I rarely shoot at high apertures or directly at the sun, it hasn't been a big issue for me. I just consider it to be like lens flare and shoot to avoid it.

I was not sure what it was when I first saw it, but this is the strangest flare that I have seen, and the light source, the sun, was not even in the frame. It was almost directly overhead though, and I did not have a hood.

What amuses me is that as stills cameras and lenses get progressively better at suppressing flare, movie makers are busy adding fake flare back in to their CGI creations to make them look more "real". The example which springs immediately to mind is the last Star Trek film, where every time a light source crept into shot you saw a great flare effect, even though in many cases these were obviously painted in after the event.